1. Field of the Invention
The present invention is broadly concerned with new dyes or light attenuating compounds for incorporation into photolithographic compositions (e.g., anti-reflective coatings and contact or via hole fill compositions) utilized in the manufacturing of microdevices. More particularly, the light attenuating compounds comprise at least two reactive functional groups and are especially useful for absorbing light at wavelengths of from about 180-450 nm. Through these functional groups, the compounds can chemically bond with a polymer binder already present in the composition or can be polymerized with a precursor polymer to form a polymer binder for use in the composition without negatively affecting the spectral properties of the light attenuating compound.
2. Description of the Prior Art
Anti-reflective coatings (ARC) have long been used in semiconductor manufacturing to control standing waves and critical dimensions (CD) of the patterned photoresists used in microlithography. As the feature size on semiconductor devices continue to decrease, CD control becomes very critical.
Currently available compositions for use as ARC""s in submicron microlithography typically comprise an organic polymer binder and an ultraviolet dye that is attached to the polymer binder by a functional group on the dye. This functional group is usually part of a conjugated, electronic structure that is responsible for the light absorbing properties of the dye. However, since reactions of the functional group alter the electronic structure of the dye, undesirable spectral shifts generally result when the dye is attached to the binder. Furthermore, a reduction in the light absorbing abilities of the dye may also occur if the functional group degrades (e.g., oxidizes) during the attachment reaction. Similar problems occur when the dye is incorporated into the polymer binder in a linear fashion using two-point attachment via two functional groups on the dye.
Thus, there is a need for a dye which can be attached to or polymerized with a polymer binder for incorporation into an ARC with minimal impact on the light absorbing abilities of the dye.
The present invention overcomes these problems by broadly providing a dye or light attenuating compound which can be incorporated into ARC""s without negatively affecting the dye""s light-absorbing abilities.
In more detail, the inventive dye has the structure of Formula I or Formula II.
Formula I 
Formula II 
wherein:
each cyclic group can be the same or different groups and is preferably individually selected from the group consisting of aromatic groups (with benzene rings being the most preferred aromatic group);
m=0-30, preferably 0-15, and more preferably 0-6;
each R1 is individually a reactive group such as those selected from the group consisting of xe2x80x94OH, xe2x80x94COOH, xe2x80x94NH2, xe2x80x94COORxe2x80x2 (with Rxe2x80x2 being an alkyl group (preferably C1-C8)), xe2x80x94CHxe2x95x90CH2, and epoxy groups;
preferably all but one ring member of the cyclic group has an R2 bonded thereto, and each R2 is individually selected from the group consisting of hydrogen, alkyls, heteroalkyls, aryls, heteroaryls, ethers, thioethers, carboxylates, cyanos, halogens, Rxe2x80x3xe2x80x94Cxe2x95x90Nxe2x80x94, Rxe2x80x3xe2x80x94Nxe2x95x90Nxe2x80x2 (with Rxe2x80x3 being hydrogen or an alkyl group (preferably C1-C8)), dialkylaminos, diarylaminos, and one of the following: 
xe2x80x83or 
where n=0 or 1
in structure A, where EWG and R3 do not form a cyclic unit:
EWG is an electron-withdrawing group such as those selected from the group consisting of carbonyls, cyanos, iminos, carboxylic acids, carboxylic esters, carboxamidos, carboximidos, and sulfonyls; and
R3 is selected from the group consisting of hydrogen, alkyls, heteroalkyls, aryls, heteroaryls, carbonyls, cyanos, iminos, carboxylic acids, carboxylic esters, carboxamidos, carboximidos, and sulfonyls; and
in structure B, EWG and R3 form a cyclic electron-withdrawing unit which includes one or more groups selected from the group consisting of carbonyls, cyanos, iminos, carboxylic acids, carboxylic esters, carboxamidos, carboximidos, and sulfonyls, and
in either Structure A or B, (*) indicates the point of attachment of R2 to the cyclic group.
Even more preferably, the dye has the structure depicted in Formula III.
Formula III 
wherein each n=1-30, and preferably 1-10, and each R1 is individually a reactive group such as those selected from the group consisting of xe2x80x94OH, xe2x80x94COOH, xe2x80x94NH2, xe2x80x94COORxe2x80x3 (with Rxe2x80x2 being an alkyl group (preferably C1-C8)), xe2x80x94CHxe2x95x90CH2, and epoxy groups, with xe2x80x94OH groups being particularly preferred.
Examples of particularly preferred Structures B where EWG and R3 form a cyclic electron-withdrawing unit include the structure depicted in Formula IV.
Formula IV 
wherein each R1 is individually a reactive group such as those selected from the group consisting of xe2x80x94OH, xe2x80x94COOH, xe2x80x94NH2, xe2x80x94COORxe2x80x2 (with Rxe2x80x2 being an alkyl group (preferably C1-C8)), xe2x80x94CHxe2x95x90CH2, and epoxy groups.
In each of the foregoing dye structures, the reactive functionalities (i.e., the R1 groups) are electronically isolated from the light-absorbing portion (i.e., the cyclic group) of the structure so that spectral shifts and degradation are minimized or avoided when the dye is polymerized, crosslinked, or otherwise reacted. Additionally, it will be appreciated that the R1 groups can be selected to react with, for example, aminoplast, polyepoxide, polyisocyanate, or polycarboxylic acid crosslinking agents, thus allowing for the design of a wider variety of polymer classes for incorporation into ARC""s for use at wavelengths of about 180-450 nm.
In the embodiment illustrated in Formula IV, the dye comprises a blocked functionality on its light absorbing moiety which allows for selective dissolution in organic solvents or aqueous media. For example, the structure of Formula IV will hydrolyze in the presence of photogenerated acids (such as acids formed in photoresist layers upon exposure of the layer to ultraviolet light) to form a base-soluble carboxylic acid. Thus, because the developer is typically a base, the resulting ARC will be etchable and subsequent plasma etching will not be necessary.
The inventive dyes can be physically mixed with a polymer binder and crosslinking agent and dissolved in a solvent system to form a composition useful for forming an ARC which can absorb at a defined wavelength or can exhibit broadband absorption (e.g., at 193, 248, and 365 nm). However, it is particularly preferred that the dye be bonded to the polymer binder. In the latter instance, the dye can be bonded to a functional group on the polymer binder or it can be polymerized with precursor polymers (preferably by step-wise methods to form linear polymers) without interfering with the spectral properties of the dye. That is, the absorbance at a wavelength of from about 180-450 nm of an ARC comprising an inventive dye bonded to or polymerized with a polymer binder is at least about 25%, preferably at least about 35%, and more preferably at least about 50% of the absorbance of the dye alone (i.e., of the dye when it is not bonded to or polymerized with another compound).
In applications where the dye is polymerized with a precursor polymer, the polymerization reaction preferably results in bonds being formed between the precursor polymer and the R1 groups on the dye structure. The resulting polymer can be incorporated into an anti-reflective composition and should have a weight average molecular weight of from about 20,000-100,000 Daltons.
Preferred precursor polymers include those selected from the group consisting of polyesters, polyacrylates, polyheterocyclics, polyetherketones, polyisocyanates, polyhydroxystyrene, polycarbonates, polyepichlorohydrin, polyvinyl alcohol, oligomeric resins, and mixtures thereof. Suitable solvent systems comprise solvents selected from the group consisting of ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether acetate, ethyl lactate, N-methylpyrrolidone, gamma-butyrolactone, tetrahydrofurfuryl alcohol, cyclohexanone, butyl acetate, diglyme, and diacetone alcohol.
The anti-reflective composition can be applied to the surface of a substrate (e.g., silicon wafer) according to conventional methods (e.g., spin-coating) to form an anti-reflective layer. The layer can then be baked, preferably at a temperature of at least about 160xc2x0 C., after which a photoresist layer can be applied to the anti-reflective layer. The photoresist layer can then be exposed to light at the desired wavelength followed by developing of the layer and subsequent etching of the developed layer according to known processes.
Advantageously, anti-reflective layers formed according to the invention have superior spectral properties. For example, at wavelengths of from about 180-450 nm, the anti-reflective layers have a molar extinction coefficient of at least about 10,000 L/mol-cm. The anti-reflective layer also has a k value of at least about 0.25, and preferably at least about 0.30 at a wavelength of about 365 nm. Finally, anti-reflective layers formed according to the invention are essentially non-subliming at temperatures of at least about 100xc2x0 C., preferably at least about 150xc2x0 C., and more preferably from about 160-220xc2x0 C. after baking on a hotplate under conventional conditions (e.g., baking at about 160xc2x0 C. for about 30 seconds).
When used in reference to Formulas I-IV, the term xe2x80x9ccompoundxe2x80x9d is intended to refer to the actual compound represented in the particular Formula, as well as all functional moieties thereof. Thus, xe2x80x9ccompound of Formula Ixe2x80x9d also refers to, for example, moieties of Formula I which are bonded to a polymer binder in an anti-reflective coating composition.